Investigating the AIE and water sensing properties of a concise naphthalimide fluorophore

A simple naphthalimide fluorophore NAP-H₂O was designed and synthesized. Basic photophysical properties were investigated, especially found that the probe showed robust green fluorescence in water compared with that in various organic solvents, and the specific mechanism was conformed to be the aggregation induced emission (AIE) through dynamic light scattering (DLS) analysis, solid-state luminescence and fluorescence imaging. Accordingly, the capability of NAP-H₂O for water sensing was examined, and good linear relationships between fluorescence intensities at the green emission band and the water content were obtained, enabling quantitative detection of water in organic solvents. The detection limits were calculated to be 0.004 % (v/v) in ACN, 0.117 % (v/v) in 1,4-dioxane, 0.028 % (v/v) in THF, 0.022 % (v/v) in DMF and 0.146 % (v/v) in DMSO, respectively. In addition, the probe presented fast response time within 5 s to water and good photostability. Furthermore, the probe was successfully applied for fast and naked-eye detection of water in organic solvents via test papers. This work provides a rapid, sensitive and naked-eye method for trace amount detection of water in organic solvents and has potential for practical applications.